Restrict Incoming Mail to SpamFilter System

Hello Everyone,

We have a multi domain Zimbra deployment with a MTA/LDAP replica and a Mailbox/MasterLDAP. The MX records for all domain are set to point to a spam-filtering system. We would like to restrict incoming (delivery) mail only from the spam-filtering system but still allow users to use SMTP Auth and send with their email clients. How might we accomplish this? Your help is greatly appreciated.

We are looking for the same answer. Single server with single domain. We have an upstream SPAM/Anti-virus filter service and would like to limit all incoming messages to the subnet of that service. Page 47 of the Open Source Edition 8.0 Administration Guide references this type of configuration but does not say how to implement it. Thanks in advance for any guidance on this quesiton.

Set iptables on your MTA to block all incoming access to port 25 except for AS/AV gateway/appliance or

Go to Zimbra Admin | Configure | Global Settings | MTA, and then set "Inbound SMTP Hostname" to your AS/AV appliance hostname/ip address. Excerpt from it's setting : If your MX records point to a spam-relay or any other external non-zimbra server, enter the name of that server in "Inbound SMTP host name" field.